I am currently tracking my 997 C4S with stock wheels and Michelins. My question is as follows.......how would my car perform with a set 20 inch techarts formulas with Michelins PS2's.

 

It would perform worse. I have a 997S and bought a set of CCW forged wheels and Toyo R-comp tires for the track.

18x9 front 245/40/18
18x12 rear 305/35/18

Wheels and tires shipped from CCW in Daytona with tires mounted/balance with tax $4300

 

I have a C4, but not the S, everything I have heard from others the 20" wheels will make the car handle worse, hence the reason you don't see race cars with 20" wheels! What I have been told the 18" wheels are the best for tracking I currently sport SP2 on my car with PSS9 and H&R sway-bars pretty impressive handling, all set-up by Sharkwerks.

 

WAYYYY worse...mainly due to the HUGE amount of wieght added...the car will brake less efficiently, turn less efficiently, and accellerate...yup...less efficiently...


As others have said, 18 is absolutely the optimal size for tracking.

 

it would perform like POS.
you want the smallest wheel that you can clear the brakes. that will make your gearing lower and less unsprung wt. everything will be better.

you dont see F1 cars with 20" wheels....

 

20 inch techart forumulas have to weigh about 40 lbs each. that will hurt. 19's are good too, they have a bigger contact patch than 18's and are just as effective if not more (depending on the application). Depending on your driving style 20's wont kill you though, if you are a noob (which I have to assume you are somewhat judging by the thread title) then just go out and get a feel before you go buying all different sets of wheels and such.

that way, when you get something better, you'll notice the difference. Most people at HPDE's dont drive fast enough to even test 20 inch PS2's max.

 

if you want looks an perf, go 19..but 18 is absolutely the preferred performance size...your contact patch can be just as big and you have less rotational mass...never a bad thing.

 

You can get 19's in the same ballpark weight as 18's and diameter and width combined are the number 1 factor in increasing contact patch. But the smaller/ stiffer sidewall, is better. hoosier didnt start makinf 19's for no reason, 19's are just as good as 18's with the same tire. The difference in a wheels of the same kind will be small going from an 18 to a 19 inch.

And tire pressure are not always straight forward, you can lose contact patch on wider wheels if you go with low low PSI in the tires. As long as yo ucan fit a decent size tire on the car 19's will not hurt you.

Porsche doesnt use them for show, they know they can use them and not lose anything.

 

The only thing I argue...is why does no racing team use 19s? Didnt say they were ****, but have really yet to find someone saying they are equivalent...dunno, I guess this is a agree to dissagree...

 

The aggressive negative camber on race cars (many 4.0, 4.5) means they need more rubber, the ride height as well, is less permitting since the cars are still based on street cars through homologation. 18's fit all of the criteria for a race car, where 19's do not, you cannot get enough rubber to run those cambers they do and run the ride height you want with 19's. More rubber also means more cushion and racing wheels get bent easily at the speeds they are going.

But for many of us who run moderate neg. camber and still run low profile tires, there is no harm no foul. You wont lose anything by going with 19's if they arent much heavier.

 

arg...that be the difference...cause on the Pcar...I cant run 19s...


but shhh...18s are still stronger!

 

18's are stronger. that's the truth. And I wouldnt want 19's either, for the simple fact that they do affect your turning radius, and since the 996 TT was designed for 18's that's what I'll get, but I did see some nice 997 TT's and GT3's at PCA with 19" hoosier R6's though.

 

well, I never said 19s werent sexy...haha

 

Interesting debate. I've had this discussions with a recently graduated engineer with a master's degree in aerospace engineering (his thesis was the impact of the GT3 wing on the downforce of a 996) with extensive experience in Motorsports and a retired engineer that graduated #1 in his class at Columbia who also races Porsches.

It is not clear cut that the smaller wheel is "better". The techincals are over my head but the wider contact patch of larger wheel is a positive when looking at the differences.

The good news for me is the recent graduate is joining us in our new shop and existing aftermarket parts business and the retired engineer is also a close friend that will help our endeavors with his expertise. It's always good to have smart friends.

In summary, heavychevy's points is validity and the "smaller tire is better theory" is not always supported with proven data.

 

just to be "the dick"...better is relative...the wheels are stronger, cheaper and weigh less...the tires are also generally cheaper...so if a 19 can hold snuff to an 18...but is signif more expensive...thats like saying...I can mod a e46m3 to out race a stock gt3 etc or the civic faster than an m3 stuff...